Providing a high level of tracking visibility when articles, e.g. mailed items, packages, cargo etc., are transported by vehicles is a task which has been faced for a long time. Such articles may be easily lost or stolen if accidentally unloaded, left behind or misplaced. With a higher tracking visibility of the articles it is possible to reduce the number of lost or stolen articles.
Various individual sensors for tracking an article have been on the market for quite some time. One approach to the problem are finder systems that have been developed, wherein an alarm RFID tag is fastened to an article and sounds when commanded by a signal, such as a radio signal, from an alarm control station. When the article is lost, a signal is broadcast from a base station to activate the alarm RFID tag and sound the alarm. The article may then be found by following the sound of the alarm RFID tag.
While article finder systems can be a great help in finding lost articles, the article finder systems are typically used in reaction to a loss of a single article and not in a manner to prevent the loss of a multitude of articles. Typical of the article finder systems is the need to manually initiate an action to find the lost article. Additionally, the article finder RFID tag requires a power source such as a battery to continuously power a receiver and to power an alarm or transmitter. The article finder RFID tag ceases to function when its battery dies, rendering it useless.
Instead of locating a single article after it has been lost, it is preferable in many circumstances to prevent the loss of an article or, even better of a multitude of articles. Thus, a tracking system that signals when an article is removed from a given area, or that signals when an article is left behind, is desirable to help in preventing the article from becoming lost.